1. Field Of The Invention
This invention relates to a blind stitch sewing machine, more particularly to a sewing machine which can feed a fabric unit smoothly in a forward direction when sewing.
2. Description Of The Related Art
Referring to FIGS. 1, 2 and 3, a conventional blind stitch sewing machine includes a main housing (10) which is fixed on a machine table (9), a head housing (11), a horizontal stationary plate (12), a presser member (13), a feed dog element (not shown), a rotating shaft (14), a fabric pushing member (15) and a needle unit (16). The head housing (11) is located at one side of the main housing (10). A motor (not shown) and some necessary mechanism (not shown) are adapted to be installed in the main and head housings (10,11). The stationary plate (12) is connected securely to the lower portion of the head housing (11) and has a stitching slot formed therein. The presser member (13) is connected movably to the lower portion of the head housing (11) and can be moved to press against the stationary plate (12). The stationary plate (12) and the presser member (13) cooperatively define a fabric passage therebetween. The feed dog element presses a fabric unit (U) (see FIG. 3) against the presser member (13) in such a manner that the feed dog element can be activated to feed the fabric unit (U) for sewing. The needle unit (16) is connected pivotally to the head housing (11) and has a curved needle (17) provided thereon. The needle unit (16) is driven to pivot in order to put stitches on the fabric unit (U). The motor is coupled with the feed dog element and the needle unit (16) so as to drive the feed dog element and the needle unit (16). The rotating shaft (14) is coupled with the motor and can be driven to rotate reciprocally. The fabric pushing member (15) has a rounded end and is connected securely to the main shaft (14) in such a manner that the fabric pushing member (15) rotates synchronously with the main shaft (14). The fabric pushing member (15) can be rotated between a first position, wherein the rounded end of the fabric pushing member (15) pushes a portion of the fabric unit (U) upward and through the stitching slot of the stationary plate (12), and a second position, wherein the rounded end of the fabric pushing member (15) is away from the fabric unit (U). Accordingly, when the fabric pushing member (15) is moved to the first position, the needle unit (16) is moved pivotally so as to put one of the stitches on the fabric unit (U). When one of the stitches has been put on the portion of the fabric unit (U), the fabric pushing member (15) is moved to the second position while the feed dog element is activated so as to feed the fabric unit (U) forward in order to put a succeeding one of the stitches on the fabric unit (U).
The drawback of the above-described conventional blind stitch sewing machine is that the rotating speed of the fabric pushing member (15) from the first position to the second position is slower than the feeding speed of the feed dog element, thereby resulting in an undesired stitching pattern due to the rough forward movement of the fabric unit (U), as best illustrated in FIG. 4.